Virtually all human biological functions show rhythms which vary predictably over a period of just more than 24 hours. Control of these rhythms and their synchronisation to the normal 24-hour day depend on a specific brain region, which hence may be regarded as the body's clock.
The proper functioning of the clock enables the internal sleep-wake, core temperature and other rhythms of man to synchronise with the changing demands of the external environment and thereby to ensure optimal performance.
The period of most of these rhythms approximates, but does not equal, 24 hours and this is the meaning the applicant attaches to the term `circadian rhythms`. The biological clock must therefore be re-set every 24 hours. This phase shift to re-set the biological clock hence enables the human to adapt to changing schedules. This re-set capability is, however, subject to certain very specific constraints. Features of our modern life, like electric lighting, jet-travel across time zones and round-the-clock work schedules have imposed conditions on the human circadian timing system which stress the biological clock beyond its capacity to maintain synchronisation of the body's rhythms with the external environment.
It is known that the hypothalamus, situated at the base of the brain, contains the nerve centres responsible for the timing of circadian rhythms. It is also known that neurotransmitters, which are chemicals contained in the nerve endings of nerve cells in the brain, and by means of which the cells communicate with each other, are released by the influx of calcium ions into the nerve endings.
One of these transmitters, the inhibitory transmitter .gamma.-ammobutyric acid (GABA), which is present in a large number of nerve cells (neurons) in the central nervous system and in the hypothalamus, is known to have a large part to play in the control of human circadian rhythms.
Recently scientists have appreciated that ability to learn new information, concentration and vigilance, motor co-ordination, appetite, mood and even sexual functions is profoundly affected by disruptions of the circadian timing system. A recent US Congressional report suggest that psycho-social and physical problems resulting from circadian rhythm disruption may represent one of the major public health issues of the century.
It is an object of this invention to provide a method which it is believed will alleviate disruptions in a mammal's circadian rhythms and also to provide apparatus for carrying out the method.